1. Field of the Invention
The present invention relates to methods and apparatus for connecting coupler members to conduit sections. More particularly, the invention relates to methods and apparatus for connecting rigid, most preferably metal, coupler members to resilient conduits such as, without limitation, resilient pipe and flexible hose.
2. Description of Related Art
Conduit such as pipe or hose typically is manufactured in lengths or sections which are coupled together during construction or installation to form a pipeline. Couplers affixed to the ends of the conduit sections couple the sections together. Often, such couplers include fittings affixed to adjoining ends of adjacent conduit sections as well as mechanisms for permanently or detachably connecting the fittings to each other to form fluid-tight joints.
One type of coupling used for connecting such conduit sections, available from Röhren- und Pumpenwerk Bauer GmbH of Voitsberg, Austria, includes separate male and female coupler fittings affixed to adjoining ends of the sections as well as a clamping sleeve slidably installed behind the male fitting. The male fitting consists of a spherical shell having openings at opposite ends to provide a passage through the shell. The female fitting includes a hemispherical socket for receiving the spherical shell. The male fitting fits into the hemispherical socket of the female fitting. A rubber gasket seated in the female fitting helps to form a fluid-tight seal between the male and female fittings. The clamping sleeve includes hooks for securing the sleeve to the female fitting so as to clamp the male fitting between the clamping sleeve and the female fitting.
This type of coupling permits the conduit section connected to the male fitting to pivot up to about 15°–30° relative to a centerline of the conduit section to which the female fitting is connected. This arrangement allows for curvature in a pipeline formed using the coupling so as to adapt to terrain on which the pipe line is placed.
Often, sections of pipe used in pipeline applications are formed from polymeric materials. For example, high density polyethylene (“HDPE”) pipe is well suited for applications such as mining, road construction, fresh water systems and wastewater systems, among others. HDPE material is lightweight compared to other piping materials such as metals. HDPE pipe is durable-its resiliency provides protection against damage from external loads, vibrations and pressure surges such as water hammer. It is resistant to scale build-up as well as to damage from most aggressive chemicals and corrosive agents.
Flexible hosing is well suited to other applications. One popular type of flexible hosing includes a flexible polymeric material such as a rubber material reinforced by a woven material formed from metal, ceramic or polymer. Known applications require coupling of flexible hosing at either the suction or discharge ends of pumping systems. Tremendous amounts of thrust can be generated at the discharge ends of the sections of hosing in such applications.
The use of a rigid materials such as metal to form couplings helps to ensure the dimensional stability of the couplings and, consequently, the tightness of the seals between the coupler fittings. One drawback to the use of couplers formed from rigid materials such as metals in joining sections polymeric pipe and flexible hose is the need for a mechanism to connect the fittings to the ends of the conduit sections. Another drawback to the use of metal couplings in connection with plastic pipes and flexible hoses the lies in the difference between the thermal expansion rates of the materials forming the fittings and the conduit, which can lead to leakage between the section of pipe and the coupler fitting as the environmental temperature varies. Typically, this problem is addressed by increasing the wall thickness of the pipe or hose above the minimum required to contain the anticipated fluid pressure so as to maintain engagement between the conduit section and the coupler. There remains a need in the art for a relatively simple and inexpensive method, and for a relatively simple and inexpensive apparatus, for connecting a coupling formed from a rigid material such as metal to a section of resilient conduit.